Humidification system, and fuel cell system comprising a humidification system

ABSTRACT

A humidification system for a fuel cell system is provided, comprising a feed line for supplying cathode gas which is to be or is humidified, to a heat exchanger, further comprising a liquid supply and an eddy generator, located upstream of the liquid supply, for generating eddies in the flowing cathode gas. A fuel cell system comprising a humidification system is also provided.

BACKGROUND Technical Field

Embodiments of the invention relate to a humidification system for afuel cell system. Embodiments of the invention further relate to a fuelcell system comprising a humidification system.

Description of the Related Art

To ensure the conductivity of the membrane separating the cathode fromthe anode within the fuel cell stack, a fuel cell should be operatedwith humidified gas. A humidifier is usually used for humidifying thecathode gas supplied to the cathode, in which a water vapor-permeablemembrane separates the cathode gas to be humidified from the cathodeexhaust gas containing the moisture.

In JP 2013/036640 A, an introduction of water on the upper side of anair humidifier is provided. This air humidifier includes spiral-shapedswirling structures in its interior, thereby swirling the air flowingfrom below, thereby resulting in improved moisture absorption.

The fuel cell system of U.S. Pat. No. 6,579,637 B1 comprises a swirlingstructure within a water separator which effects a separation of waterparticles in suctioned air. However, it is only used to reduce theliquid in the exhaust gas flow.

Furthermore, solutions with an injection nozzle for atomizing the waterare known from DE 10 2015 220 093 A1, DE 10 2015 204 620 A1 and DE 102014 223 906 A1. However, the introduction of water at the top of ahumidifier or the use of injection nozzles can lead to problems in afrost start of the fuel cell system due to ice formation. The injectionnozzle is also formed from a plurality of components, or requires theuse of further components, and is therefore very complex in terms ofequipment.

US 2013/004866 A1 shows a fuel cell system in which the liquid wateraccumulating on the anode side is brought to the cathode side in orderfirstly to humidify the cathode gas flow and secondly to be able toconduct too much liquid out of the fuel cell system under the influenceof gravity.

U.S. Pat. No. 6,309,770 B1 describes a solid oxide fuel cell which hasanode recirculation into which a heat exchanger and a condenser and acombustion chamber are integrated.

DE 10 2013 003 599 A1 describes a further fuel cell system in which theliquid water arising on the anode side is introduced into the cathodegas on the cathode side downstream of a humidifier in order to bringabout saturation of the membrane there.

SU 947 578 A1 describes an air humidifier in which, in order to protectagainst icing, the inflowing air is guided in a spiral-shaped wallbefore it enters the actual chambers of the housing. A steam tube ispresent in the actual chamber.

DE 11 2016 000 888 T5 describes a system for exhaust gas aftertreatmentwhich is designed as a double-screw mixing system. A liquid supply inthe form of an injection nozzle for supplying an additive is presentupstream of the individual screws.

DE 10 2004 022 245 A1 describes a fuel cell system with a humidityexchange module with hollow fiber membranes. These hollow fibermembranes are combined to form a bundle, wherein a means for generatingan eddy movement in the gas flow can be provided to achieve the mostuniform possible incident flow on the individual hollow fiber membranes.

BRIEF SUMMARY

Embodiments of the present invention provide a humidification systemwhich improves the input of liquid into the cathode gas. Embodiments ofthe present invention also provide a fuel cell system having such ahumidification system.

According to embodiments of the present invention, a humidificationsystem is provided having a feed line to supply cathode gas which is tobe humidified or is humidified to a heat exchanger. A liquid supply isalso provided. An eddy generator for generating swirls in the flowingcathode gas is arranged upstream of the liquid supply.

The eddy generator fluid-mechanically coupled into the feed line changesthe direction of flow of the cathode gas such that it now alsoexperiences a velocity component in the circumferential direction of thefeed line. The absolute cathode gas velocity thus increases, so that ashearing force acts between the cathode gas flowing past and the liquidwhich is provided via the liquid supply. Because of the velocitycomponent in the circumferential direction of the tube of the feed line,the cathode gas flows against the liquid, as a result of which it issucked or pressed into the interior of the feed line. The transfer ofthe liquid into the cathode gas is improved. The relative humidity inthe cathode gas is raised before entry into cathode chambers of a fuelcell stack or—if present—before entry into a humidifier, as a result ofwhich the humidifier can then be designed smaller.

In a preferred embodiment, the heat exchanger, which is formed inparticular as a charge air cooler, has an inlet nozzle or a hoodarranged on the liquid supply side. Upstream of the inlet nozzle is theliquid supply and the eddy generator. Such an arrangement isadvantageous because the cathode gas is supplied to the feed line bymeans of a compressor. Due to the compression, the incoming cathode gasis very warm, in particular at high load points of the compressor inwhich much liquid water is produced. Due to the elevated temperature ofthe cathode gas, it can absorb the liquid very well. When the liquidevaporates and is subsequently absorbed into the cathode gas, thecathode gas flow is cooled slightly, which makes it possible to use asmaller heat exchanger or charge air cooler.

Depending on the requirement, the heat exchanger in an alternativeembodiment comprises an inlet nozzle or a hood connected to the feedline, the liquid supply being connected directly or directly to theinlet nozzle.

Alternatively or additionally, the inlet nozzle is arranged lower than ahorizontally arranged center line of the heat exchanger. As a result,the feed line is also arranged lower, which may be necessary due toinstallation space requirements. In many cases, raising (i.e. in adirection opposite to the gravitational force) the liquid is notpossible due to the existing risk of frost.

Another possibility for also not having to transport the liquid upwardsis to connect the liquid supply to the feed line substantially in anorientation oriented vertically from below.

A further advantageous embodiment provides that the liquid supplycomprises a liquid basin. Such a liquid basin prevents the liquidintroduced via the liquid supply from immediately entering the heatexchanger and consequently the charge air cooler. Such accumulation ofthe liquid would drastically reduce the gas mass flow of the cathode gaspassing through the heat exchanger. The purpose of the liquid basin istherefore that the water does not flow directly from the tube of thefeed line into the heat exchanger and accumulate there. In the case of aheat exchanger, that is to say in the case of a charge air cooler, thiswould lead to an even lower flow velocity and thus to an even lowerwater discharge.

The liquid basin and/or the liquid supply can be attached directly tothe feed line or also to the inlet nozzle of the heat exchanger.However, an advantageous embodiment provides that the liquid basin isformed on the feed line and/or the inlet nozzle itself. In this respect,the liquid supply can thus be designed integrally with the feed lineand/or integrally with the inlet nozzle of the heat exchanger.

According to embodiments of the present invention, a fuel cell system isprovided comprising a fuel cell stack having cathode chambers and anodechambers, the cathode chambers of which are connected to an inlet and anoutlet of a humidifier. An anode feed line is also provided whichconnects a fuel storage to the anode chambers. An anode recirculationline connecting the anode outlet to the anode feed line is provided onthe anode outlet side. A separator, which is preferably formed as awater separator, is assigned to the anode recirculation line. Theseparator is connected to the liquid supply via a liquid line. Such afuel cell system has the advantage that the liquid collected in theseparator arranged on the anode side can be used to humidify the cathodegas before it is introduced into the actual humidifier. In this context,a pre-humidification system for pre-humidifying the cathode gas cantherefore simultaneously be seen in the humidification system.

In order to be able to regulate the extent of humidification of thecathode gas, it has proven to be advantageous if a liquid controlelement is assigned to the liquid line or is arranged therein. Thisliquid control element, formed as a flap or valve, can be controlled orregulated and have different degrees of opening.

In order to regulate the supplied fuel, it is expedient if a fuelcontrol element is assigned to or arranged in the anode feed line. Thisfuel control element can also be formed as a valve or a flap which canbe regulated or controlled and can have different degrees of opening.

In order to pre-warm the fuel supplied from the fuel storage, it hasproven to be advantageous if a heat exchanger is assigned to the anodefeed line between the fuel storage and the anode chambers or when suchis arranged in the anode feed line. In other words, the heat exchangeris fluid-mechanically coupled into the anode feed line. This heatexchanger is preferably formed as a recuperator which supplies heat tothe fuel by means of the principle of heat conduction.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Embodiments of the invention are explained in more detail below withreference to the drawings.

FIG. 1 is a schematic illustration of a humidification system which isconnected on one end to a humidifier and on the other end to acompressor (block diagram),

FIG. 2 is a schematic illustration of a fuel cell system with ahumidification system according to FIG. 1 (block diagram),

FIG. 3 is a schematic view of the detail “A” from FIG. 1 of a firsthumidification system,

FIG. 4 is a schematic view of the detail “A” from FIG. 1 of a secondhumidification system,

FIG. 5 is a schematic view of the detail “A” from FIG. 1 of a thirdhumidification system, and

FIG. 6 is a plan view of an eddy generator.

DETAILED DESCRIPTION

FIG. 1 shows a humidification system 1 of a fuel cell system 2 which isconnected only by way of example to a humidifier 4 at one end and to acompressor 10 at the other end. It is also possible to connect thehumidification system 1 directly to the cathode chambers of a fuel cellstack 3. In the present case, the humidifier 4 can be connected tocathode chambers of the fuel cell stack 3 and comprises a cathode-sideoutlet 5 via which humidified cathode gas (for example air or oxygen)can be supplied to the cathode chambers and thus to the cathodes of thefuel cell stack 3. The humidifier 4 also has a cathode-side inlet 6 viawhich humidified cathode exhaust gas from the fuel cell stack 3 can besupplied to the humidifier 4. The humidifier 4 also has an exhaust gasoutlet 7 connected to an exhaust gas line 29 as well as a gas inlet 9connected to a feed line 8 for the cathode gas which is to be humidifiedor is already (pre-) humidified. A compressor 10 is assigned to orfluid-mechanically coupled into the feed line 8. Cathode gas is drawn inthrough the compressor 10, introduced into the feed line 8, and suppliedto a heat exchanger 13 or the humidifier 4 in compressed form. Upstreamof the heat exchanger 13 and downstream of the compressor 10, a liquidsupply 11 is provided for pre-humidifying the cathode gas before it issupplied to the fuel cell stack 3 or the humidifier 4. As a result ofthe compression of the cathode gas by means of the compressor 10, thetemperature of the cathode gas rises, so that a larger quantity ofliquid can accumulate in the cathode gas.

The humidification of the cathode gas is additionally improved by aneddy generator 12 arranged upstream of the liquid supply 11, arranged inthe present case between the compressor 10 and the liquid supply 11. Theeddy generator 12 generates eddies in the flowing cathode gas. In otherwords, the cathode gas flow through the eddy generator 12 experiences avelocity component in the vertical direction or circumferentialdirection of the tube of the feed line 8, whereby the liquid provided bythe liquid supply 11 is sheared and mixed with the cathode gas.

The cathode gas enriched with the liquid is conducted to the heatexchanger 13, in the present case to a charge air cooler, which has acompressor-side inlet 14 or a hood arranged on the compressor side. Inother words, the liquid supply 11 is therefore upstream of the inletnozzle 14 of the charge air cooler. It is also possible to arrange theliquid supply 11 on the inlet nozzle 14 or the hood of the heatexchanger 13 itself.

FIG. 2 shows a fuel cell system 2 with a humidification system 1. Herethe cathode-side outlet 5 of the humidifier 4 is connected via a cathodefeed line 24 to cathode chambers of a fuel cell stack 3. In addition,the humidifier 4 is also connected by its cathode-side inlet 6 to thecathode chambers via a cathode exhaust gas line 26 through whichunreacted cathode gas or humidified cathode exhaust gas is returned tothe humidifier 4. The cathode gas is supplied via the cathode chambersto the cathodes of the plurality of fuel cells arranged in the fuel cellstack 3. Proton-conductive membranes separate the cathodes from theanodes of the fuel cells, wherein fuel (e.g., hydrogen) may be suppliedto the anodes via anode chambers. For this purpose, the anode chambersare connected to a fuel storage 17 providing the fuel via an anode feedline 18. Fuel not reacted at the anodes can be recirculated to the anodechambers via an anode recirculation line 19. Preferably, a recirculationblower, not shown in greater detail, is in this case assigned to theanode recirculation or is fluid-mechanically coupled into the anoderecirculation line 19. In order to regulate the supply of fuel, a fuelcontrol element 23 is assigned to the anode feed line 18 or is arrangedin the anode feed line 18. This fuel control element 23 preferably takesthe form of a pressure control valve. Upstream of the pressure controlvalve, a heat exchanger 24 is provided, preferably in the form of arecuperator for (pre-)heating the fuel.

Disposed in the anode circuit in the present case is a separator 20,preferably a water separator, through which liquid can be collected. Thedrain of the separator 20 is connected to a liquid line 21 whichconnects the separator 20 to the liquid supply 11 of the humidificationsystem 1. Thus, the liquid generated on the anode side is used on thecathode-side for humidification—or pre-humidification, if a humidifier 4is used—of the cathode gas. In order to be able to adjust the quantityof liquid provided by the liquid supply 11, a liquid control element 22is assigned to the liquid line 21 or is fluid-mechanically coupled intoit. This liquid control element 22 thus enables the preferablycontrollable supply of the liquid from the separator 20 to the cathodecircuit.

In FIG. 3 , the detail A from FIG. 1 is shown in a first humidificationsystem 1. In this case, the inlet nozzle 14 of the heat exchanger 13, inparticular of the charge air cooler, is arranged at the level of ahorizontally arranged center line 15 of the heat exchanger 13. Theliquid supply 11 is connected to the feed line 8 substantially in anorientation oriented vertically from below, so that no liquid drips fromabove into the tube of the feed line 8. Instead, the liquid provided bythe liquid supply 11 is carried along by the cathode gas flowing pastdue to shearing forces acting between the liquid and the cathode gas. Inorder to increase these shearing forces, the schematically illustratededdy generator 12 is provided upstream of the liquid supply 11. Thisswirls the flow of the cathode gas, so that even more liquid is carriedalong by the cathode gas flowing past and enters the inlet nozzle 14 ofthe heat exchanger 13. The humidified cathode gas is cooled in the heatexchanger 13. The cooled, humidified cathode gas may then be directed tothe cathode chambers. Alternatively, however, it can also be supplied tothe gas inlet 9 for cathode gas to be humidified at a humidifier 4.

The heat exchanger 13 or the charge air cooler according to FIG. 4differs from those according to FIG. 3 in that the inlet nozzle 14 orits connecting piece connected to the feed line 8 is arranged lower thanthe horizontally arranged center line 14 of the heat exchanger 13. Atthe same time, the hood is correspondingly asymmetrically shaped. As aresult of the lowered arrangement, the liquid of the liquid supply 11does not have to be guided upward to such an extent, which leads to areduction in the risk of frost. It can also be seen that the eddygenerator 12 according to FIG. 4 has a smaller dimension than that ofFIG. 3 .

FIG. 5 shows an alternative example of detail A in which a liquid basin16 is assigned to the liquid supply 11. The basin is formed by acorresponding shaping of the feed line 8 so that the liquid basin 16 isformed on the feed line 8. In other words, the liquid supply 11 is thusformed integrally with the feed line 8. The liquid surface 27 past whichthe cathode gas flows can be increased through the use of the liquidbasin 16. The fill level in the basin or the liquid surface 27 can bevaried by the actuation of the liquid control element 22. The use of theliquid basin 16 also ensures that no liquid accumulates in the region ofthe hood of the heat exchanger 13, which would make the heat exchanger13 more inefficient. The transition from the basin to the feed line 8and/or the transition to the inlet nozzle 14 of the heat exchanger 13preferably takes place without buckling, so that a correspondinglysmooth transition is formed. The feed line 8 is formed in the region ofthe basin with a cross-section that is larger than in its remainingregion, so that the cathode gas can exert the largest shear forcespossible in the circumferential direction on the liquid.

FIG. 6 shows a plan view of an eddy generator 12, the externaldimensions of which are adapted to the internal dimensions of the feedline 8. The eddy generator 12 is rigidly mounted in the tube of the feedline 8. In other words, the eddy generator 12 is formed as a stator.When the cathode gas flows past blades 28 of the eddy generator 12, thecathode gas is swirled and experiences a velocity in the circumferentialdirection of feed line 8. A cathode gas flow can be humidified by thisarrangement.

In general, in the following claims, the terms used should not beconstrued to limit the claims to the specific embodiments disclosed inthe specification and the claims, but should be construed to include allpossible embodiments along with the full scope of equivalents to whichsuch claims are entitled.

The invention claimed is:
 1. A humidification system for a fuel cellsystem, comprising: a heat exchanger including a charge air coolerhaving a feed line, the feed line including a tube for supplying a flowof fresh cathode gas which is to be or is humidified to the heatexchanger; a liquid supply arranged upstream of the heat exchangerrelative to a flow direction of the flow of fresh cathode gas, theliquid supply connected to the feed line from below and such that, inuse, no liquid drips from the liquid supply into the feed line; and aneddy generator rigidly mounted in the tube, wherein the eddy generatorincludes a stator located upstream of the liquid supply relative to theflow direction of the flow of fresh cathode gas, wherein the eddygenerator is configured to generate swirls in the flow of fresh cathodegas such that the flow of fresh cathode gas experiences a velocitycomponent in a circumferential direction of the tube and a shearingforce acts between the flow of fresh cathode gas and a liquid providedby the liquid supply.
 2. The humidification system according to claim 1wherein the heat exchanger includes an inlet nozzle arranged on theliquid supply side, and the liquid supply is upstream of the inletnozzle.
 3. The humidification system according to claim 2 wherein theinlet nozzle is arranged so as to be lower than a horizontally arrangedcenter line of the heat exchanger.
 4. The humidification systemaccording to claim 1 wherein the heat exchanger has an inlet nozzleconnected to the feed line, and the liquid supply is connected to theinlet nozzle.
 5. The humidification system according to claim 1, whereinthe liquid supply is connected to the feed line substantially in avertically oriented orientation from below.
 6. The humidification systemaccording to claim 1, wherein the liquid supply comprises a liquid basinand the eddy generator is configured to generate swirls in the flow offresh cathode gas such that the flow of fresh cathode gas experiences avelocity component in a circumferential direction of the tube and ashearing force acts between the flow of fresh cathode gas and a liquidprovided in the liquid basin, resulting in evaporation of liquid intothe flow of fresh cathode gas from the liquid basin.
 7. Thehumidification system according to claim 6, wherein the liquid basin isformed on the feed line or on an inlet nozzle of the heat exchanger. 8.A fuel cell system, comprising: a humidification system including: aheat exchanger including a charge air cooler having a feed line, thefeed line including a tube for supplying a flow of fresh cathode gaswhich is to be or is humidified to the heat exchanger; a liquid supplyarranged upstream of the heat exchanger relative to a flow direction ofthe flow of fresh cathode gas, the liquid supply connected to the feedline from below and such that, in use, no liquid drips from the liquidsupply into the feed line; and an eddy generator rigidly mounted in thetube, wherein the eddy generator includes a stator located upstream ofthe liquid supply relative to the flow direction of the flow of freshcathode gas, the stator located downstream of a compressor relative tothe flow direction of the flow of fresh cathode gas; wherein the eddygenerator is configured to generate swirls in the flow of fresh cathodegas such that the flow of fresh cathode gas experiences a velocitycomponent in the circumferential direction of the tube and a shearingforce acts between the flow of fresh cathode gas and a liquid providedby the liquid supply; a fuel cell stack having cathode chambers andanode chambers, the cathode chambers connected to an inlet and an outletof a humidifier; an anode feed line connecting the anode chambers to afuel storage; an anode recirculation line; and a separator assigned tothe anode recirculation line and to a liquid line connecting theseparator to the liquid supply.
 9. The fuel cell system according toclaim 8 wherein a liquid control element is assigned to or arranged inthe liquid line.
 10. The fuel cell system according to claim 8 wherein aheat exchanger is assigned to or arranged in the anode feed line betweenthe fuel storage and the anode chambers.